Begin by accessing the Workable API to extract the data you need. Workable provides a RESTful API that you can use to programmatically retrieve candidate data, job listings, or other relevant information. You'll need to authenticate using an API key, which you can obtain from your Workable account settings. Use an HTTP client (like `curl`, Postman, or a Python script using `requests`) to perform GET requests to the API endpoints to fetch the necessary data.

Once you've fetched the data from Workable, you need to parse it. The data will typically be in JSON format. Use a programming language of your choice (such as Python, Node.js, or Java) to parse this JSON data. Make sure you structure it in a way that's suitable for the Firestore document format, which involves key-value pairs.

If you haven't already, create a Google Cloud Platform account and set up a new project. Enable the Firestore API for your project. You'll also need to configure billing, as Firestore usage beyond the free tier may incur costs. This setup will allow you to utilize Firestore to store your data.

To interact with Firestore from your application, install the Firebase Admin SDK. This will allow you to authenticate and perform operations on your Firestore database. For example, in a Node.js environment, you can install it using npm:
```bash
npm install firebase-admin
```
Similarly, you can find installation instructions for other languages in the Firebase Admin SDK documentation.

You need to authenticate to your Firestore database using service account credentials. Download the service account JSON file from your Google Cloud Console under the IAM & Admin section. In your application, initialize Firestore with these credentials. Here is a sample setup in Node.js:
```javascript
const admin = require('firebase-admin');
const serviceAccount = require('path/to/serviceAccountKey.json');

admin.initializeApp({
credential: admin.credential.cert(serviceAccount)
});

const db = admin.firestore();
```

Before uploading the data to Firestore, ensure it is transformed to fit Firestore's format. Consider how you want to structure your Firestore documents and collections. This may involve organizing your data into multiple collections or documents and setting appropriate keys.

Finally, write a script to upload your parsed and transformed data to Firestore. Use the Firestore SDK methods to create new documents and collections. Here's a basic example in Node.js:
```javascript
const data = /* your parsed and structured data from Workable */;

data.forEach(async (item) => {
const docRef = db.collection('your-collection-name').doc(item.id);
await docRef.set(item);
});
```
Ensure each document is correctly inserted with the right structure and data integrity.

By following these steps, you can efficiently transfer data from Workable to Google Firestore without relying on third-party connectors or integrations.